Cellulose acetate method of laminating



Patented Dec. 8, 1931 UNITED STATES PATENT O F LOUIS BARTELSTONE, OFFLATBTTSH, NEW? YORK, ASSIGNOR, BY MESNE ASSIt'i-Ilt'lfllllil'Tfl, TOELBEE HOLDING CORPORATION, 01' WILMINGTON, A CORPORATION or DELAWARECELLULOSE ncnm'rn METHOD or LAMIN'ATINO No Drawing. Original applicationfiled .Tune 8, 1926, Serial No. 118,580. Divided "and this applicationilled June 3, 1926.

This invention is devoted specificall to laminatedv glass and theprocess of ma 'ng it wherein the glass surfaces are conditioned throughthe agency of a 'film of cellulose 5 acetate; this application being adivision of my second copending application Serial No. 113,580 filedJune 3, 1926, disclosing the use of both the nitrate and the acetate ofcellulose, and being also a continuation in n part ofmy firstapplication Serial No.

7 29,069 filed July 30, 1924, and patented December 14, 1926, No.1,611,139,.Said latter application setting forth my basic discoverythatv through a proper employment of an expressed vegetable oil ofinsignificant solvent action on celluloid (castoroil being in-- factthat they are each transparent, and flexible, and such methods as wereknown'seemed to indicate that they manifested properties incompatiblewith mutual adhesion. Consequently, in laminating celluloid and glasssheets, it has been customary for-others always to condition the surfaceof the. glass by '65 an initial application 'of a solution of cellu-'loid; avoiding attempts to use solutions of cellulose acetate under thebelief that the lat 7 ter was incompatible with the celluloid sheet,although it was recognized that cellu- 40 lose acetate might be expectedto exhibit centain optically-desirab l e superior characteristics if itcould be used as a conditioning agent.

I have discovered, however, that by draw ing upon the variousdiscoveries set. forth in easilyevaporated to produce a tough lm of sayin the neighborhood of 1/1000 of an inch.

Serial N0. 113,581.

my two previousapplications, it is possible to bring about an adhesionsufficiently tenacious to answer for many purposes, although perhaps notquite equalling the extraordinary degree of adhesion obtainable asrecitedin my earlier application and in my second application withrespect to the use of cellulose nitrate. g In carrying out my processwherein cellulose acetate is used forconditionin-g the glass 65preparatory to carrying out the ultimate laminating steps, the materialwill first be applied to the glass in the form of a solution. Thesolution which I have found most satisfactory is readily obtainable onthemarket; being. known commercially asso-called air plane dope andwhich consists primaril' of cellulose acetate dissolved in various sovents which admit of being quickl and cellulose acetate freeffrom-anyeasily inflammable ingredients such as camphor or similar plasticizingingredients used in making cel- -luloid like material. This solutionpos-- sesses considerable viscosity and may be applied to the glasssurface either by spraying or other spreading methods and in asufiicient amount so that when ultimately dried the film of celluloseacetate will be quite thin,

The drying may be accomplished spontaneously or it may be hastened byputting the prepared glass in heated cabinets for a sufiicient period oftime to eliminate the solvents.

The non-vitreous laminating elements may be a sheet of highrgradecelluloid or of other organic transparent material and, to removesuperficial grease o; dirt from its surface, which would tend to inhibitadhesion, it is preferably sprayed with a solution of a cellulosecompound or preferably with a solution of celluloid. The se flexiblesheets are then submitted to anair-bathor other conven-' tional' meansfor expediting evaporation of the solvent.

gravitate away until it has in large part 1 oozed out from between thesheets. The super-imposed sheets are then transferred to the platen ofan appropriate press, preferably hydraulic, and the temperature of thelaten is maintained in the neighborhood of 220 F. For 3-ply laminatedsheets which 100 pounds to the'square inch. It is then total about a inthickness it is recommended that the pressure be increased step by stepuntil it' has obtained approximately maintained at that pressure for saysix minutes or so; whereupon the press may', opened and the hotlaminated plate removed.

It will be found that the laminations are ad-' hering with greattenacity. For 5-ply glass consisting of two' sheets of celluloid andthree sheets of glass, which may total a thickness of about 1", thepressure should be gradually increased step 'by step until it totalsabout 200' pounds to the square inch and it is then maintained for abouteight minutes at a :temperature of say 220. This will suffice toaccomplish a'good adherence between the laminations even though,ordinarily speaking, it would be supposed that the celluloid could-notbecaused to adhere strongly'to the film of cellulose acetate which coatstheglass surface. p

Having thus. revealed this invention, I claim as new and desire tosecure the followin combinations and elements, or equivalentsUnitedthereof, by Letters Patent of the States 1. An article ofmanufacture comprising two panes of glass; an intervening sheet of vcelluloid; and intermediate transparent films of a camphor-freecellulose acetate, said films being in immediate contact with the innerglass surfaces.

2. A process of conditioning a surface of glass for subsequentlycementing it to a surface of celluloid, said process comprehendingthedeposition on said glass surface of a thin liquidfilm of celluloseacetate free from camphor and then converting said liquid film into afilm of solid cellulose acetate free from volatile matter.

3 3. An article in the nature of laminated glass comprising externalpanes of glass; an intervening sheet of flexible transparent material;and a solid film of cellulose acetate intermediate each of thecontiguous surfaces, said film of solid cellulose acetate beingdeposited directly upon the glass surface and a cellulose acetate beingcemented to the contiguous surface of the flexible sheet.

4. An article of manufacture comprisin two panes of glass; anintervening sheet 0 flexible transparent material; and intermediatefilms of a compound of cellulose and an organic acid radical, said filmsbeing transparent and free from volatile matter and in immediate contactwith the innerglass surfaces. v v

5. A- process of conditioning a surface of glass for subsequentlycementing it to a surface of anorga'nic flexible sheet, said processcomprehending the step of coating said glass surface with a' thin liquidfilm of a solution of cellulose acetate, and then evaporating allsolvent and volatile matter from said liquid film to convert it into afilm of solid cellulose acetate. 6. An article in the nature oflaminated glass comprisingexternal panes of glass; an intervening sheetof celluloid; and a film of free from camphor intermediate each of theconti ous' surfaces, said film of cellulose acetate eing depositeddirectly upon the glass surface and cemented to the'contiguous surfaceof the flexible sheet.

7. An article of manufacture com rislng twopanes ofglass, an intervenings eet of celluloid surfaced by an'evaporated film of celluloid; andintermediate films of cellulose acetate free from volatile matter, saidfilms being in immediate contact-with the inner glass surfaces. M

' 8.' A process of laminating glass consisting in first conditioning theinner surfaces of the glassbydepositing thereon thin liquid films of asolution of cellulose acetate; then evaporating the solvent from saidliquid film to convert it into a solid film; and then through the agencyof. a vegetable oil and under heat and pressure bringing said preparedsurfaces into intimate contact.

' 9. An article of manufacture comprising two panes of glass; anintervening flexible sheet of substantial thickness composed ofcellulose acetate; and intermediate transparent films of athicknessapproximating a process comprehending the application to.

said glass surface of a film of a cellulose acetate solution free fromcamphor-like ingredients and of such thickness that when 7 subsequentlydried into a solid form it will yield a' film free from volatile matterand havinga thickness approximating a 1/1000 of an inch. p

11. A process of laminating glass consisting of first conditioning theinner surface of the glass by initially filming it with a solution ofcellulose acetate free from camphor; then evaporating the solvents toproduce a solid film; and then through the agency of an expressedvegetable oil causing said prepared surface to adhere to an interveningflexible transparentsheet through the aid of heat and pressure.

In witness whereof, I have hereunto subscribed my name. LOUISBARTELSTONE.

